This study is designed to aid in the evaluation of clinical disease activity in patients with idiopathic inflammatory myopathies, a diverse group of diseases that include inflammation in skeletal muscle. Since the pathology includes primary muscle capillary endothelial cell damage, we are seeking markers of activation and injury to endothelial cells and activation of coagulation factors, including complexes of thrombin-antithrombin, plasmin-antiplasmin, tPa, and thrombomodulin. In selected patients, we are also evaluating markers of platelet activation and release. It is anticipated that these assays will help in developing a noninvasive, comprehensive clinical assessment tool of disease activity.